Enhancement of the photoconductivity in 2D photonic macroporous silicon structures

Abstract

Effects of the enhancement of photoconductivity in 2D photonic macroporous silicon structures were investigated. Dependence of photoconductivity on the angle of incidence of the electromagnetic radiation is observed with maxima at normal incidence of electromagnetic radiation, in the region of the angle of full internal reflection respective to macropore walls and at a grazing angle of incidence respective to the surface of structure. The absolute maximum of photoconductivity is measured at distance between macropores, corresponding to two lengths of the electron free run, i.e. by the maximal transfer of the amplified electric components from a macropore surface in a silicon matrix. Angular dependences of photoconductivity, as well as enhancement of the photoconductivity in comparison with monocrystal silicon, primary absorption p-component of electromagnetic radiation testified to formation of surface electromagnetic waves in illuminated macrporous silicon structures. Its effects result in amplification of a local electric field on a surface of macroporous silicon structure and a macropore surface. The measured value of the built-in electric field on a macropore surface achieves 1 06 V/cm, the signal of photoconductivity amplifies 1 02 times, and Raman scattering -up to one order of value.

Coherent oscillations in IR spectra of 2d macroporous silicon structures with surface nanocoatings

“…The resonant maxima are stored for 20 seconds after switching off the illumination. This is 200 times longer that of macroporous silicon structures without nanocoatings [20].…”

“…The resonant electron scattering results in the infinity growth of dielectric constants and corresponding changes in IR absorption at room temperature. The big scattering time is needed to make possible generation of well-separated oscillations [20]. If the scattering time is much bigger than the lifetime of the most stable state, then the oscillation has some minima ( Fig.…”

“…According to [18], the phonon damping effect leads to an additional shift towards the phase behavior. Paper [20] deals with the influence of impurities on the Wannier-Stark ladder and calculation of the width of the Wannier-Stark ladder levels E due to scattering from impurities. The Wannier-Stark ladder is not broken by impurities if the intervals between the transitions due to scattering from impurity atoms with lifetime  are bigger than the period of electron oscillations in external field.…”

“…The Wannier-Stark ladder is not broken by impurities if the intervals between the transitions due to scattering from impurity atoms with lifetime  are bigger than the period of electron oscillations in external field. In [20], the following estimate of the probability W for an electron to leave the state per unit time due to scattering from an impurity atom at lattice site was obtained: W < 2V 0 Ni/(Nh), where V 0 is the impurity potential, N i the impurity concentration and N  (a 2 ) -1 the density of states. As a result, the inequality  /T B > 1 passes to N i < E/(4a 2 V 0 ).…”

“…The presence/absence of resonance scattering of an oscillating electron in an electric field at the potential of an impurity surface state with quantum Wannier levels is controlled at room temperature by the resonant maximum of the IR absorption, which is 200 times longer than that of macroporous silicon structures without nanocoatings [20]. Thus, we proposed the high coherent optical quantum computer based on a macroporous silicon structure with the surface layer of nanocrystals for the implementation of the quantum electro-optical effect of Wannier-Stark [27].…”